In a basic communication system a simple communication network is provided, which can link together two communication terminals so that the terminals can communicate with each other in a communication session or call. Conventionally, a designated entity in the network uses a stored tariff to determine a charge for a call based on the call's duration, or for a service based on the service provided. Each terminal user has a charging account with the operator of the network. The charge for a call is then allocated to the charging account of the user of the terminal that originated the call.
The 3G Partnership Project (3GPP) is defining a reference architecture for the Universal Mobile Telecommunication System (UMTS) core network which will provide the users of user equipment (UE) with access to various services. This UMTS core network is divided into three principal domains. These are the Circuit Switched domain, the Packet Switched domain and the Internet Protocol Multimedia Subsystem (IMS) domain.
The IMS network makes sure that multimedia services are adequately managed. The IMS network supports the Session Initiation Protocol (SIP) as developed by the Internet Engineering Task Force (IETF). SIP is an application layer signalling protocol for starting, changing and ending user sessions. A session may, for example, be a two-way telephone call or a connection between a user and an application server (AS). The establishment of these sessions enables a user to be provided with services. One of the basic features of SIP is that the protocol enables personal mobility of a user using mobile UE by providing the capability to reach a called party (which can be an application server AS) via a single location independent address.
For third generation (3G) communication systems the systems of more than one operator may be used for carrying a call and operators of all of those systems may be able to levy charges independently for the services they provide in supporting the call. In an IMS network charging functionality is based on the IMS network nodes reporting accounting information in messages that include an IMS charging identity (ICID). The ICID provides a unique identifier for each call, which enables charges for a single call to be made to the correct account by a number of operators. Accordingly, current charging functionality employing the use of ICID only relates to charging for a single call or connection.
It is possible however, for a user to simultaneously establish communication with more than one destination. For example using the explode mechanism, it is possible for a user to send a message to a plurality of destinations. An explode indication could be inserted to various SIP methods (e.g. MESSAGE). To send an SIP message to multiple destinations, the SIP message includes a URI (Universal Resource Indicator) list specifying the destinations. A Request-URI of the message contains a ‘list’ parameter that points to the part of the message that carries the URI list. A specialised application server receives the request and sends a similar message to each of the URIs in the list. Each of these messages contains a copy of the payload included in the original message.
There is currently no feasible solution for efficiently managing charging for a session including use of a plurality of resources based on the use of ICIDs. The present invention aims to provide such a solution. A further aim of the present invention is to provide a way of managing charging when a plurality of different messages are generated in a single session.